Jaszczak R J, Gilland D R, Hanson M W, Jang S, Greer K L, Coleman R E
Department of Radiology, Duke University Medical Center, Durham, NC 27710.
J Nucl Med. 1993 Sep;34(9):1577-86.
We describe a technique using a line source and a rotatable air-copper-lead assembly to acquire gamma transmission computed tomographic (TCT) data for determining attenuation maps to compensate SPECT emission scans. The technique minimizes problems associated with discriminating 99mTc transmission and 201Tl emission photons and requires only a modest increase in total study time. A 99mTc line source and a stacked foil ("multislat") collimator are placed near the focal line of a fan-beam collimator (114 cm focal length) mounted on one detector of a triple-camera SPECT system. We acquired TCT data of plastic rod and anthropomorphic thorax phantoms to investigate the capability of the line source and rotatable air-copper-lead attenuators to determine attenuation maps. The data were acquired with and without 5.4 MBq (145 microCi) of 201Tl placed in the myocardial chamber of the thorax phantom. Phantoms also were scanned using a curved transmission slab source mounted to a parallel-hole collimator. Fan-beam TCT images have improved resolution compared with parallel-beam TCT images. Two patient scans also were performed to evaluate the clinical usefulness of fan-beam TCT. The rotatable air-copper-lead attenuator method eliminates contamination of emission data by transmission photons and reduces spill-over of emission data into the transmission energy window for some cases. Results show the feasibility of using fast, sequential or interlaced transmission scans of a line source within a rotatable air-copper-lead attenuator assembly to obtain accurate attenuation maps for SPECT attenuation compensation.
我们描述了一种技术，该技术使用线源和可旋转的空气-铜-铅组件来获取伽马透射计算机断层扫描（TCT）数据，以确定衰减图，从而补偿单光子发射计算机断层扫描（SPECT）发射扫描。该技术将与区分99mTc透射光子和201Tl发射光子相关的问题降至最低，并且只需要在总研究时间上适度增加。一个99mTc线源和一个堆叠箔（“多板”）准直器放置在安装在三相机SPECT系统一个探测器上的扇形束准直器（焦距114厘米）的焦线附近。我们获取了塑料棒和人体胸部模型的TCT数据，以研究线源和可旋转空气-铜-铅衰减器确定衰减图的能力。在胸部模型的心肌腔中放置5.4 MBq（145微居里）的201Tl和不放置的情况下获取数据。还使用安装在平行孔准直器上的弯曲透射平板源对模型进行扫描。与平行束TCT图像相比，扇形束TCT图像具有更高的分辨率。还对两名患者进行了扫描，以评估扇形束TCT的临床实用性。在某些情况下，可旋转空气-铜-铅衰减器方法消除了透射光子对发射数据的污染，并减少了发射数据溢出到透射能量窗口中。结果表明，在可旋转空气-铜-铅衰减器组件内对线源进行快速、顺序或交错透射扫描以获得用于SPECT衰减补偿的准确衰减图是可行的。
